build: split ceph_ver.h

build: split ceph_ver.h

Split ceph_ver.h into:
1) ceph_ver.h containing git-related macros
2) ceph_release.h containing just human written ceph version number /
   ceph version name.

The benefit is that denc.h which needs to know CEPH_RELEASE value
can skip including git-related macros. There are many compilation units
that use denc.h and only few that need git-related macros.
Reduces amount of files to recompile after SHA1 changes.
It is only relevant for developer environment.

Signed-off-by: Adam Kupczyk <akupczyk@ibm.com>
(cherry picked from commit 1a56293f2c890d9222fab5e1e91c34e2d864aef9)